In theory, not very.
The most infamous of the late Ming taxes were what's the known as the Three Payments (
三餉), so named because they were instituted to fund payments fo the army. From contemporary and Qing era history works such as the Veritable Records of Ming and the History of Ming, we know these were:
遼餉 (Liao Pay) - fund the defence of Liaodong against the rising Manchurian menace.
剿餉 (Pacification Pay) - fund the suppression of peasant revolts that had been breaking out
練餉 (Training Pay) - levied in the wake of devastating Manchurian invasions in 1638
These primarily took the form of a tax on farmlands. The Liao Pay was the most significant of these, being originally raised in 1618, and quickly increased thrice to 0.9 candareen by 1620. In 1631, it was further raised to increased to 1.2 candareen. The Pacification Pay was levied in 1637 until 1639, when it was replaced by the Training Pay at about 1.4 candareen.
The Liao Pay returned some 6.6 million taels, and another million from various minor taxes on commerce. The Training Pay added 7.3 million taels. Each tael was equivalent to 100 candareen. To put the tax number in perspective, consumer prices according to the 1593 journal
- One kati of noodles: 0.7 candareen
- One sho (1% of a dan) of rice: 0.8 candareen
- One kati of beef: 1.3 candareen
- One kati of pork: 1.8 candareen
- One live duck: 3 candareen
- One live goose: 18 candareen
For reference, each mu of land (the basic land tax unit) had a basic production level of at least 2 dan of rice or equivalent each year. Other taxes such as customs were also low at only 1/30, or 3.33%. Therefore, the nominal tax value was in fact extremely low, especially in comparison to the double digit income tax of modern western societies.
Relatively speaking, these taxes represented a 50% increase over regular government revenues. However, this is due to how incredibly low normal taxes were. The subsequent Manchurian dynasty of Qing levied taxes of up to 5 candareen per mu, for example.
In practice, the peasantry were heavily exploited by an utterly corrupted bureaucratic machinery and social inequality. At every stage of governance, bureaucrats lined their own pockets with "tax" money. Every tael of tax from the provinces entailed several times more money extracted from the peasants to enrich the middlemen. More seriously, the wealthy in late Ming society could bribe and cajole tax collectors into passing their share of the tax burden onto less influential peasants.
This corruption was extended to the tax system as well where local magnates bribed officials to hide the amount of land or property they owned in order to keep their taxes low. Then, when the state was forced to increase taxes for military expenses, the costs were simply passed along to the peasants.
- Swope, Kenneth M. The Military Collapse of China's Ming Dynasty, 1618-44. Routledge, 2014.