These days, when for most people their paycheck comes in form of a check/bank transfer, and most charges (including Tzedakas) are done via credit card, what is the ideal way to give “separate” Maaser? Is, by making sure the Tzedakas given during the month equals the amount of Maaser required, enough?
Maaser need not be given on money that is in front of you.
You can give Maaser by donating from your credit card every time you receive a check/bank transfer, or, you can do this once a month, as you wrote.
Ideally, Maaser should be separated immediately when income is received, i.e. when the check clears. A good way to do this is by opening a separate Maaser account for Tzedaka and depositing your Maaser immediately into the separate Tzedaka account to distribute later.
Nonetheless, Maaser may be computed at fixed times during the year. It is preferable to compute your Maaser in six-month units than annually. The accounting of Maaser should not be carried over from one year to the other, just like Maaser Tevuah and Maaser Beheimah may not be separated from produce and animals of one year for the other year.
If you haven’t yet received your paycheck, or if the check hasn’t cleared yet, and you wish to give on future income, see here:
Can Maaser be given in advance? If not, can one give Maaser for funds received in a check before depositing it? If not, what about after depositing it, before it has been processed (e.g. Mobile deposit, transaction pending, etc.).
It should be noted that every time you donate to Tzedaka by using a credit card, Tzedaka will only end up getting a percentage of the actual funds. It is still considered as though you gave full Maaser. However, it is obviously better to give them a direct wire or a check which usually means that Tzedaka will receive more, unless you are giving it to them via a fundraiser who usually will take a “larger slice” than the small credit card fee.