Why your deposits aren't your sales
Processors take their fee before they pay you. A $100 sale at 2.6% + 15¢ arrives as $97.25. If your books count the $97.25 as your sales, your income is too low, the $2.75 fee is never counted as an expense, and your sales won't match the 1099-K the processor sends to the IRS, which shows the full $100.
How to get it right
Record the full sale as income and the fee as an expense. Your processor's payout (or transfer) report has both for every deposit. In Square it's under Reports, then Transfers; in Stripe it's under Balance, then Payouts.
Is my rate normal?
Divide a month's fees by that month's card sales. Small, in-person sales usually run close to the advertised percentage; lots of tiny sales or keyed-in cards push it up because of the fixed fee on each one.