As you might expect, I provide allowance in cash, at least the first 3-6 meetings. if I think she will be sticking around for a while, I might offer to send her cash by Zelle or even PayPal. Yes there is some risk to this, but I have that mitigated.  
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When I do provide cash, I like to use $20's. It makes a nice visual offering to her to get a decent sized stack of Jacksons. And I can always hit an ATM if I deplete my pocket cash from sugar payments.  But once in a while, I don't have that much in 20's on me and I don't want to go out to an ATM. So on a few occasions I have pulled out some $50's and/or $100's to pay. But doing that makes me wonder if my SB perceives getting big bills differently then getting smaller bills. Is there some inherent "wow" experience from getting 3 or 4 hundred dollar bills? Will she (erroneously) think that I am "more rich" if I use $100's then if I use $20's? Will that embolden her to hit me up for more allowance or additional cash for some imaginary emergency thinking I can "afford it"?  
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Of course, $400 is $400 no matter the size of the bills. I suppose I could give her 400 $1's and see how that goes. What if, as an experiment, I try to give her rolled quarters? That would be 40 rolls weighing  20 lbs!  
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Anyway, just musing as I pass my time in solitary confinement waiting for my Philippina Unicorn to land at LAX on Saturday...
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Life is good.
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The Cat

... I, too, prefer providing $20 bills when I make a donation. I find it a total pain in the ass when I receive $100 bills in an ATM. If I can't immediately deposit them in my account or have a teller break them down into smaller denominations, it's aggravating having to try to spend one in a retail establishment -- although easier in restaurants, it's true... I always assume providers find it somewhat troublesome as well.  Just my .02. Or $100...

Years ago, I guess on Newbie or General, someone mentioned that they mix it up: 3 Benjamins + 5 Jacksons = 400. That gives her something to spend easily and immediately and a smaller stack to stuff in her purse, pocket or bra.

I too get miffed when I get $100s instead of $20’s from the ATM.  I have found that my SBs don’t like them because they can’t use them as easily to pay for routine expenses.  I try to give them one $100 bill and the rest in $20s to make it a little more palatable.  Otherwise, I use the $100 bills at self checkout where I can get change back. My bank got rid of tellers months ago. Everything is ATM now.

I just assumed that 100s were more impressive and conveyed more of a cachet that this is a high end luxurious undertaking we're participating in.  A stack of 20s just feels sleazy to me, idk, maybe I should try it.  My SBs always seem happy with the large bills though.

Many ATMs now dispense 100's as a default for larger withdrawals. I usually modify the payload to a mix of 20's, 50's, and 100's.  And about 3 years ago I started a little routine when I get one or more 100's in my wallet. When I get home, I stash the 100's for later, and then never actually grab the stash. I've accumulated a tidy stack now and I consider it my emergency cash for disasters (or trips to Vegas .  
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Life is good.
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The Cat

Or at least I did before the lockdown. I will pull some money out of the bank and go to the casino, if I win or even if I don't actually win, but I have at least five grand or so left over from the night, I'll keep the money as "Charlie Harper" money and I won't go back to the casino or to the bank/ATM until I've spent it all, and then I will "wash, rinse and repeat" lol

I'm part of the $100 bill club.  It seems to me awkward for the SB's to stand there counting the money in front of you.  Or do they trust you and go their happy way?  For me it is just easier having a thinner wallet or to grab the $100's from my pre-placed location to give her before she leaves.  But I am open to new experiences, so next time it will be 15-20 President Jacksons!  

I've only had one or two who counted in front of me. But I suspect they were UTR pros or semi-pros so no big deal.  
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And I have only had one (recently) ask for cash upfront. But I'd met her a few weeks back at a strip club known for extras. Even though we discussed a SD/SB option for us, she had a hard and fast menu for take out the day I met her and never deviated from it.  I was hoping after two-three weeks of the club being shut down, she'd be more amenable to a sugar-deal as opposed to a pure pro-play. Alas, she was going right down the hooker script, including watching the clock - which annoyed the hell out of me. Where the fuck did she need to be?  
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So I just went with it and unloaded a week's worth of backlog into her mouth...
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Um... It's possible I forgot to tell her before I took the shot...
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And I think I was pushing her head down rather aggressively...  
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Perhaps I was preoccupied with her poor manners? :p  Anyway...  
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Life is good
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The Cat

Krugerrands? Maple Leafs? ... Anyone paid with "hard" currency?  
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If she knows the value of 1/10 or 1/4 ounce of gold, she only has to count to one.

I do the same with both 50s and 100s, but I used them.

I NEVER allow an SB or provider to count money in front of me. It's bad behavior. Out they go.

So you just finished with them.  They still have some jizz dripping out or down their chin.  As you’re leaving you give her a tribute.  She counts it.  What you’re going to stop her?  
Some girls have trust issues ...... no wait all these girls have daddy issues and trust issues.  

Not while I'm standing there, she doesn't. Out.

I got tired of going to the ATM each time. Seems like I'm there a lot. I started just doing venmo or zelle when trust is built.

Lots of the younger (pretty much anyone graduated from high school or under 30) folk I know just Venmo, ApplePay, etc everything.  
But I haven’t done the Sugar Daddy thing ever.  
So, I’m amazed that no one here has said a SB has requested Venmo.  
Now there is a potential negative. But it also sounds like it could be a positive.  
The person to person transaction limit in Venmo is 299.99.  
Just a thought.

Had a few SB’s request a payment by app as I'm sure most on here have had a few times, but I don’t use them. If they don’t want cash I move on. Plus, it means a SB actually has to meet to get payment. There are SB’s who no-show, just like normal dating sites and providers. Any SB’s looking for on-line only but pretend they will meet need to use apps. As I’m looking for in-person, this helps weed these out when early on I say don’t use apps.

I’ve started to use Venmo more and more for other things. Because there are so many similar names I always have the person check the name with me in person to make sure the money goes to the correct ID.  
You can just say it adds a level of security to ensure that they are the person the ID represents.
Still, you should stick with whatever makes you most comfortable.